Extensively treating petroleum distillates



' July 18, 1950 c. A. COHEN ExTENsIvELY TREATING PETROLEUM DISTILLATES Filed Jan. 4, 1947 Patented July 18, 1950 EXTENSIVELY TREA'IAING PETRQLEUM DlSTILLATES vCharles A. Cohen, Roselle Bark-N. .1., assignor to Standard Qil ADevelopments.C011ll12lny, i a corporation ofDelaware applica-tion January 4, 1947,1'seria1N0. 720,293

'Thisiinvention relates to an improved process `for v.the vpreparation of stable highly refined. min- ;.eral oils and ofv oil-soluble petroleum sulfonates `and in particular, to an improved process for 4the Apurification of the oil solublesulfonates obtained as .i Eby-,products in the preparation .of mineral In-the :preparation of White oil products, a 'petroleumbase stock usually of` Mid-Continent or aGulf .Coastorigin is exhaustively treated with sulfuric acid, 'that is, a distillate usually of lubricating oil range :is treated with acid of between 96%. strength and 30% fuming acid .and with a volume .relative .to the oil of between .about V15 and about 50%. The acid is usually applied to the oil in several small quantities and ithe .heavy .sludge phase separated before the subsequent addition of acid. After the separation of the heavy sludge resulting from the iinal treatment with .the acid, the oil is highly colored due to the presence of nely dispersed sludge throughout the oil. Highspeed centrifuges are f.ceminonly employed to `separate this finely divided sludge, commonly knovvn as pepper sludge, from the oil prior to neutralization. By

The present invention is an improvement over lsuch=processing especially in regard to the removal of the finely divided sludge.

The oil after sludge separation is normally neutralized withv an alkaligenerally 'in the case of mineral White oilstocks, with an aqueous solution of sodium carbonate. The neutralized oil is then treated with an aqueous alcoholic solution containing between about and 50% alcohol, usually of either ethyl or isopropyl alcohol. 'Ihe oil after neutralization is usually steamed to remove alcohol and Water. The aqueous alcoholic solutions, especially those of higher alcohol content, remove from the oil substantial quantities of oil-soluble sulfonates. The color` of the solution depends largely upon the degree of separation of the sludge from the oil prior to neutralization. The present invention is concerned particularly with the removal of sludge from the oil prior to aqueous alcoholic washing as a particular means of improving the color of the oil and of the sulfonates obtained from the aqueous alcoholic solutions.

When high speed centrifuges are employed for the separation of sludge, the oil which over- 3 Claims. (Cl. A19E-4Q) flows from the centrifuge generally contains, 56

1when the sulfonate content of the .oil is about l0 grams per 100 cc., `from 1 to 2% of nely divided. suspended sludge. It has now been found Athattt'his small quantity of finely divided and nely dispersed sludge may be separated from theoil prior to neutralization by recycling into the feed to the centrifuges or other such equip.-

.ment for separating pepper sludge, 20% to 80% and preferably about an equal volume of VWhat is commonly termed an intermediate .neutral oil. Il'iy the term, intermediate neutral oil, is meant -an `acid treated oilfrom which the sludge #has been separated by. such commonly available meansas the centrifuge and then which has been subsequently neutralized, then treated with an aqueous alcoholic solution and finally steamed.

aA further improvement in sludge removal may be obtainedby adding to the oil prior to this fine sludge iseparatioma small quantity of lter aid.

The .effectivenessof the recycling procedure appears to be .connected with a sulfonate dilution effect. .While the amount of pepper.sludge retained in the oil is roughly proportional to the Aamountof sulfonic acid dissolved in the oil, a directproportion cannot be drawn. For example, anacid oil having a sulfonic acid concentration of vfrom approxi-mately 10-12 grams .of sulfonic acid per 100 cc. generally contains from .1 to '2% of suspended sludge after centrifuging an acid oil after heavy sludge separation. On the other fhand, if V.the acid oil prior to centrifuging is dilutedfwith an oil of about the same boiling range in-Whichabout 5 or 6 grams of sulfonic acid per 100.cc.,v-concentration occurs, 'it has been found Ythat on centrifuging, the oil mixture contains less than 0.1% by volume of sludge. Based on the original sulfonic acid content, the sludge has therefore been reduced from about 10 to 20% by volume of sludge on the sulfonic acid to about l to 2% by volume of sludge. With proper dilution and conditions of operation a sludge content based on the sulfonic acid content of less than 1% may be obtained.

As a speciiic illustration of this invention a flow diagram is presented in the drawing, A heavily acid treated oil containg about 2% suspended sludge and l0 grams of sulfonic acid per cc. of oil enters through line 2, mixing equipment I0, in this particular case an agitator. Into this agitator is also passed through line 4 a quantity of neutralized 'and Washed oil. The mixture of acid oil, sludge and neutral oil overflows the agitator I0 through line l2 into centrifuge 20 whereby the sludge is separated through line 22 to a sludge collecting drum 24. The clear sludgefree oil is discharged from the centrifuge through line 26 to a surge drum 28. The oil is then passed through pump 29 and supplied to an SO2 stripping tower 32 through line 30. Vacuum is applied to the tower through `a barometric jet and condenser 34 to remove SO2 from the oil through line 36. The SO2-free oil is collected in drum 38, passed through pump 40 and supplied to an agitator 42. Also passedinto the agitator 42 through line 49 by means ofV control valve 50 into a soap drum 52. The sulfonate solution is removed from soap drum 52 by means of line 53 for further processing and purication as desired. The neutralizedand substantially sulio-v nate free oil overflows through line 54 into steam heated preheater 56 whereby it is brought to proper temperature for steam stripping to remove the alcohol present in a small amount in the oil leaving the preheater through line 58.

The oil then passes to the stripping tower 60 through spray head .62. Steam is fed in sufcient quantity and pressure through line 04 and spray head 66 to 'maintain a temperature of about 120 C. in the oil leaving the stripping tower through line 68.

Alcohol and water are recovered overhead from the stripping tower through line 10, are Vcondensed in cooler l2, and sent to storage through line 13. The oil leaving the stripping tower 60 through line 68 is fed by pump 14 to a dehydrating tower 80 through line 16 and spray head 18. p

Air, which may be preheated, is fed to the bottom of the tower through line 82 and distributor 84 and a small amount of moisture present in the oil is removed by this means and vented to the atmosphere through line 86. The oil leaves the dehydrating tower through line 88 through cooler 90 where it is reduced to the proper temperature and thence to surge drum |00 through line 92. Treated oil is recirculated from surge drum |00 through pump |02 to the agitator |0 for purposes of diluting the sludge containing oil. From surge drum |00 treated oil is also continuously withdrawn through line |04 to storage.

The eiiicacy of the recycling procedure of this invention can be gauged by comparison of the colors of sodium sulfonates extracted from the oil by the processings ofl the prior art and the method of the present invention. By processings not involving the recycling of the intermediate 4 neutral oil a color of 5.5 red on the Lovibond Tintometer was obtained in ra 7% (wt.) sulfonate dilution in a Water-white mineral oil. On the other hand, the sodium sulfonate extracted from the same oil which had been previously diluted with 50% by volume with an intermediate neutral oiland then subjected to the same degree of centrifuging showed a color of 1.8 red for the same concentration and the same cell depth (1) Also, the oil not diluted prior to centrifuging had a pepper sludge content of 1.5% by volume while that subjected to dilution had 0.1% by v01- ume. This substantial reduction in pepper .sludge content is, moreover, not to be expected on a purely dilution basis.

What is claimed is:

1. Improved process for the preparation of a white oil product from a distillate oil boiling in the lubricating oil boiling range which has been treated heavily with acid and which contains suspended sludge particles and soluble petroleum sulonates which comprises adding to said distillate oil from about 20% to about'80% of a recycled refined oil product as defined hereinafter, centrifuging the mixture to separate sludge, washing the resulting distillate with a neutralizing agent, treating the resulting neutralized distillate with an aqueous alcohol solution to remove oil soluble sulfonate, steaming the treated distillate to pro'- duce said refined oil product, segregating said rened oil product into two portions, recycling .one portion to said distillate oil and producing a white oil product from the other portion.

2. Process as dened by claim 1 wherein about equal volumes of said recycled refined oil product are added to said distillate oil. f 1

3. Process as dened by claim 1 wherein said distillate oil contains about 2% .of a iinely divided sludge.

CHARLES A. COHEN.

REFERENCES CITED The following references are of record in the 'file of this patent:

OTHER REFERENCES Gruse et al.: Chemical Technology of Petro,- leum, 2nd ed., 1943, pages 547-8. 

1. IMPROVED PROCESS FOR THE PREPARATION OF A WHITE OIL PRODUCT FROM A DISTILLATE OIL BOILING IN THE LUBRICATING OIL BOILING RANGE WHICH HAS BEEN TREATED HEAVILY WITH ACID AND WHICH CONTAINS SUSPENDED SLUDGE PARTICLES AND SOLUBLE PETROLEUM SULFONATES WHICH COMPRISES ADDING TO SAID DISTILLATE OIL FROM ABOUT 20% TO ABOUT 80% OF A RECYCLED REFINED OIL PRODUCT AS DEFINED HEREINAFTER, CENTRIFUGING THE MIXTURE TO SEPARATE SLUDGE, WASHING THE RESULTING DISTILLATE WITH A NEUTRALIZING AGENT, TREATING THE RESULTING NEUTRALIZED DISTILLATE WITH AN AQUEOUS ALCOHOL SOLUTION TO REMOVE OIL SOLUBLE SULFONATE, STEAMING THE TREATED DISTILLATE TO PRODUCE SAID REFINED OIL PRODUCT, SEGREGATING SAID REFINED OIL PRODUCT INTO TWO PORTIONS, RECYCLING ONE PORTION TO SAID DISTILLATE OIL AND PRODUCING A WHITE OIL PRODUCT FROM THE OTHER PORTION. 